Method and apparatus for gauging sheet material



Sept. 5, 11933. R MAYNE METHOD AND APPARATUS FOR GAUGING SHEET MATERIALFiled Nov. 24, 1928 2 Sheets-Sheet 1 Sept. 5, 1933. R. MAYNE METHOD ANDAPPARATUS FOR GAUGING- SHEETIATERIAL Filed Nov. 24, 1928 2 Sheets-Sheet2 Patented Sept. 5, 1933 UNITED STATES METHOD APPARATUS FOR GAUGINGSHEET MATERIAL 7 hat-Tia yne, Akron, Ohio, assignor to The B. F.Company, New York, N. EL, a corpora- Application November 2 2, 19%Serial No. 321,625

" 5 Claims. (31. Flt-351) This invention relates to methodsand apparatusfor gauging sheet material, and especially it relates to procedure andapparatus for detecting variations of thickness in a moving sheet ofplastic material, for example, a sheet of unvulcanized rubbercomposition, as the same is continuously delivered from a rubber-workingcalender.

The chief objects of my invention are to provide a gauge of thecharacter described which will be extremely sensitive to variations ofstock thick-: ness, and which easily may be maintained in a condition ofuniform sensitivity. Another object is simplicity of structure.

Briefly stated, my invention comprises an electro-rnagnetic gauge whichutilizes magnetic flux instead of electric current as a medium forinducing electric current in a circuit which includes a recording orcalibrating device, by means of which variation of the reluctance of themagnetic circuit, caused by variation in thickness of a sheet or"material, is indicated or recorded, or is utilized for correcting theadjustment of the sheet pro.- ducing means.

Of the accompanying drawings:

Fig. l is a vertical section of a sheeting calender and my improvedgauging apparatus, in its pre- 7 ferred form, associated therewith.

Fig. 2 is a section on line 2-2 of Fig. l and Fig. 3 is a section online 3--3 of Fig. 1.

Fig. 4/is a section on line of Fig. 3.

Fig. 5 is a wiring diagram of my preferred form. of gauging apparatus.

Fig. 6 is a modified wiring diagram of my preferred gauging apparatus.

Fig. 7 is a modified form of gauging apparatus.

Fig. 8 is a wiring. diagram of my modified term or gauging apparatus.

Referring to the drawings, 10 is an end frame and 11, 12, and 13 arerespective upper, middle, and lower rolls of a three-roll calender ofusual design adapted to form a sheet of material 1% upon the roll 12from a bank of plastic material 15 in the bight of the rolls ll, 12, andto deliver said sheet onto a moving conveyor liner 16 passing beneaththe lower roll 13. A horizontal rod 17 disposed parallel to the calenderrolls is supported from its ends upon the calender frames 10, andpivotally suspended from'the rod l'l' is a gauging apparatus designatedgenerally by the numeral 18, the position of the rod 17 with rela tionto the roll 12 being such that the gauging apparatus rests lightlyagainst the plastic sheet it upon said roll.

The gauging apparatus 18 comprises a frame 19 journaled at its upper endupon the rod 17 be tween two positioning collars 20, 20, and having itslower end formed with spaced apart leg-portions 21, 21, upon which arejournaled respective wheels 22, 22, adapted to rest against the sheet14- on the roll 12.

The frame 19 supports a magnetic gauging device comprising a laminated,H-shaped, steel core member 23 secured to the respective leg members 21by screws 2 24., and so positioned thereupon that it normally isdisposed radially with relation to the roll 1,2 with the faces at oneend of its parallel portions lying closely adjacent but not touching thesheet 14 onsaid roll. The other ends oi said parallel portions of thecore are con" nected to each other by an armature 25 of mag neticmaterial secured thereto by screws 26, 26 of non-magnetic material suchas brass, spacingblocks or shims 2?, 27 of non-magnetic and pref erablynon-conductive material being interposed between the armature and therespective core portions. The thickness of the spacing blocks issubstantially the same as the gap between the surface of thecalender=roll 12 and the adjacent portions of the core. 'lIhe transverseportion or" the H-shaped core 23 is of smaller cross-sectional area thanthe parallel portions of the core, and the end portions of the latterpreferably are than their intermediate portions, as shown. for purposessubsequently to be demribeol.

The wiring oi the core 23 will best be undcrstood by reference to 5wherein 28 and are wire coils wound upon one of the 'parallei portionsof the core 23 at each side of the trans verse portion thereof, and 30,31 are similar wire coils wound upon the other parallel portion of saidcore, said coils being interconnected in series as shown. The coils Ell,are not essential to the operation of the device but are desirablebecause they provide a balanced structure. A wire coil 32 is wound onthe transverse portion of the core 23 and is connected with one coil 33of an A. C. galvanoineter or wattmeter 34 which may be positioned at apoint remote from the calender. In the simplest embodiment of myinvention,

other coil 35 of the galvanometer, which is the exciting coil, togetherwith the coils 28, 29, 30 and 31 of the core 23, are connected in seriesacross an A. C. supply line 36, the circuit being completed from theupper side of the supply line 36 through leads 136, 38 and 37, coils 28,30, 31 and 29 in series, leads 39 and 40, coil 35 and lead 137 to thelower side of supply line 36.

In the operation of the apparatus, the circuit is energized and atest-piece of correct thickness and of the material to be gauged ismounted between the calender roll 12 and the gauging device 18 to serveas a standard for adjusting the latter. The correct adjustment of thedevice produces a zero reading on the galvanometer, and an incorrectadjustment reads either way therefrom, which condition is said tobeunbalanced. If unbalanced, the circuit is brought to balancedcondition by adding to or reducing the thickness of the shims 27, whichwill alter the length of the gaps between the armature 25 and the core23. The calender may then be started and the sheet material 14 passedbeneath the gauge 18, the galvanometer 34 registering any variation inthe thickness of said sheet from the standard to which the gauge isadjusted.

The action of the forces within the gauge is as follows. The coils 28,29, 30, and 31 are so wound and arranged that when energized theyproduce magnetomotive force (M. M. F.) which is cumulative and of thesame direction, with the result that a flu); is caused to flow in a pathdefined by the parallelportions of core 23, the calender roll 12, thearmature 25, and across the gaps between the core and the calender rolland between the core and the armature. If the ratio of the M. M. F. ofthe coils 28, 30 to the reluctance of the gaps between the core 23 andthe armature 25 is equal to the ratio of the M. M. F. of the coils 29,31 to the reluctance of the gaps between the core 23 and the calenderroll 12, and assuming that the reluctance of the iron path is negligibleas compared with the reluctance of the gaps, then the two ends of thecore 23 will be of the same magnetic potential and no flux will flowthrough the transverse portion of the core. This condition is said to bebalanced and gives a zero reading on the galvanometer.

If the thickness of the sheet 14 varies from the standard to which thegauge is balanced, then the two ratios referred to in the foregoingparagraph will be different, flux will flow through the transverseportion of the core 23, and an electrical current will be induced in thecoil 32 which current will deflect the indicator of the galvanometereither by from zero according as the sheet 14 is over or under thedesired thickness.

Let us consider the action of the gauge at a particular instant, saywhen conditions are balanced, and current in the coils is flowing in thedirection indicated by the polarity of the supply-line 36 and isdecreasing. Then flux will flow through the core following the courseindicated by the full-line arrows of Fig. 5. If the sheet material 14runs below the desired thickness flux will flow in the transverseportion of the core 23 in the direction of the broken line arrowpointing to the right and current will be induced in the coil 32 and beso recorded by the indicator of the galvanometer. If the sheet material14 runs oversize the flux in the transverse portion of the core willflow in the opposite direction as indicated by the reversed arrow andinduce a current to flow through the coil 33 of the galvanometer in theopposite direction from the preceding case,

and thus cause the galvanometer to register an oversize condition of thesheet.

The relatively small cross-section of the transverse portion of the core23 limits the. induced current flowing to the galvanometer to a safevalue to prevent damage to the galvanometer coil when "the gauge islifted from the work while energized.

The gauge isadapted to operate'upon stock of any thickness and alwayscan be brought to balanced condition either by the aforementioned methodof varying the reluctance of the gaps between the coil 23 and armature25, or by my preferred method of varying the M. M. F. of one of thecoils of the core with relation to a coil on the other side of thetransverse portion thereof. The latter method may be carried out byvarying the number of turns of one of the coils with relation to theother by means of a dial switch, suitable circuits for effecting suchadjustment being shown in Figs. 5 and 6 of the drawings.

The preferred method of balancing the gauge by means of a dial switch isillustrated in Fig. 5 wherein the leads 38 and 40 are eliminated, andthe lead 37 carried to contact 41 of one of a series of contacts 41, 42,43, and 44 of a two-blade dial switch 45. Taps 46, 4'7, and 48 takenfrom successive turns of the windings of the coil 28 are carried to thecontacts 42, 43, and 44 respectively. The dial switch is provided with asecond series of contacts 49, 50, 51, 52 connected respectively to thelead 39 and to taps 53, 54, and 55 taken from alternate turns of thewindings of the coil 29 immediately at one side of the lead 39. Oneblade of the switch 45 is adapted to make contact with the contacts 41,42, 43 and 44 and is connected-to one side of the A. 0. supply line 36.The other blade of the switch 45 is adapted to make contact with thecontacts 49, 50, 51, and 52 and is connected to that side of the coil 35of the galvanometer 34' which is connected to the lead 40 in the simplerform of the circuit.

The arrangement is such that when the blades of the switch are on thecontacts 41, 49 the turns of wire utilized in the coils 28, 29 are ofequal number. When said blades are on the contacts 42, 50 there is adifferential of one turn in favor of coil 28. In like manner the otherpositions of the switch blades increase the differential of turns in thecoils 28, 29 so that the latter will produce different magneticpotentials to offset the different reluctances of the gaps between thecore 23 and calender roll and the core and armature when stocks ofvarious thicknesses are to be gauged. This circuit has the advantageover the balancing method embodying changes of shims in that theadjusting means may be more conveniently situated, remote from thecalender, and adjustment is more easily and quickly eifected. Thiscircuit also provides constant uniform sensitivity in the gauge byvarying the flux to compensate for Variations in the length of the airgap between the core and calender, since variations in the length ofsaid air gapnormally would vary the sensitivity of the gauge.

The gauge rests lightly against the work and magnetic pull on the gauge,toward the calender roll, is reduced by the provision of the enlargedend portions on the core-legs adjacent the work, since magnetic pull fora given flux is inversely proportional to the area of the air-gap. Theenlarged portions on the opposite ends of the corelegs are to provideuniformity of structure only.

The modified circuit-shown in Fig. 6 is of simpler construction thanthat shown in Fig. 5 and 190 provides the same advantages of remotecontrol and easy adjustment as the latter, but does not provide constantuniform sensitivity.

In the circuit shown in Fig. 6, considering one instantaneouscondition,the positive side of the supply line 36 is connected through lead 138 tothe coil 30 and thelatter connected in series with coils 31, 29 and 28and taps 60, 61, 62,

and 63 are taken from the final turns of thelatter and connectedrespectively toicontacts 64, 65, 66 and 67 of a single-bladedial-switch, the blade 68 of which is connected by the lead 69 to thefield or exciting :coil of an A. C. galvanometer 34, the other side ofsaid coil being connected' through lead 139 to the negative side of thesupply-line 36. It will be obvious that the number of taps taken fromthe coil 28 may be greater or fewer than the number shown according tothe requirements of the installation.

The arrangement is such that the number of turns in the coil 28 may bevaried to vary the magnetomotive force of the coil 28 to compensate forthe different reluctances in the magnetic path occurring when a stock ofdifferent thickness is calendered and gauged.

.The modified gauge shown in Fig. 7 is substantially oi the sameconstruction as the preferred structure shown in Figs. 1 to 4 inclusive,except that it is provided with a compensating armature 70 standingclear of the core 23 and provided with means by which said armature maybe moved toward and away irom the core to vary the length of the gapsbetween said armature and the ends of the parallel portions of the core.

Mounted upon opposite sides of the parallel portions 01 the core 23 attheir ends which are remote from the work, are outstanding brackets suchas the brackets '71, 71 of Fig. 7!, said brackets being connected by across piece 72 through the middle of which is threaded a screw 73., Theouter end of the latter is provided with a hand wheel 74, and its innerend is formed with an enlarged flange or bead revolubly seated inacomplemental recess in the armature '70 and retained therein by athreaded 1 without the use of spacing shims.

The wiring of "the modified gauge shown in Fig. '1 may be slightlydiflerent irom the wiring of the preferred form. As shown in Fig. 8, the

coil 32" on the transverse bar of the armature 23 is the exciting coilof the device, one side of said coil being connected through lead 140 tothe positive side of the supply-line 36 considering one instantaneouscondition, and the other side of said coil being connected in serieswith one side of the fleld-cofl 35 of the galvanometer 34', the otherside 01' said field coil 35 being connected through lead 141 to thenegative side of the suptly-nne 36 Coils 28 29 30 and 31 are wound onthe'respective paralnometer.

lel portions of the core 23 and connected in series to each other, andto the potential coil 33 of the galvanometer 34", as shown.

The arrangement is such that when the coil 32 is energized, two coursesof magnetic flux are established, one across the gaps between thearmature and calender roll, through the calender roll, through thetransverse portion of the core and through the intervening corestructure, and another through the transverse portion of the core,through the armature 70, across the 'gaps between the latter and thecore, and

through the adjacent parallel portions of the core, both courses beingindicated by arrows in Fig. 8. The result is that an alternating voltageis induced in the coils 28 29 30 and 31 and the cumulative voltages ofthe coils 28 30 is in opposition to the cumulative voltagesof coils 2931 When the device is balanced, that is when the reluctance of the gapsbetween the calender roll 12 and the core 23 is the same as thereluctance of the gaps between the calender roll 12 and the core 23 thenthe flux divides equally in the two courses mentioned, and the resultantinduced voltage is zero, and therefore no current flows in the circuitcomprising the coils 28 29 30 31 and the coil 33 of the gait/a Thisgives a galvanometer dial-reading of zero.

When the reluctance of the gaps between the core and calender rollvaries, due to changing thickness of the material being calendered, theflux does not divide equally and therefore induces a voltage in thecoils 29 31 which is greater or less than the voltage induced in thecoils 28 30", with the result that an electrical current, which iseither approximately in phase or approximately 180 degrees out of phasewith the main current, flows through the galvanorneter coil 33 andcauses the indicator of the latterto deflect one way or the other fromthe neutral zero position.

Other modifications are possible within the scope or the appendedclaims, and I do not limit the claims to the exact procedure or specificconstruction shown and described.

I claim:

1. Apparatus for measuring the thickness of sheet material, the saidapparatus comprising magnetic circuit means having a gap therein and amagnetic shunt across the gap, means for producing a flux in saidcircuit, means for varying the width of the gap according to variationsin the thiclmess of the sheet, material, and means including a coilassociated with said shunt for manifesting variations of the fiuxtherein resulting from the variations in the width of the gap.

2. Apparatus as defined in claim 1 in which the shunt is of such smallmagnetic conductivity as to avoid the induction of an electric currentin the coil of such strength as to cause damage to the manifestingmeans.

3. Apparatus for measuring the thickness of sheet material, the saidapparatus comprising magnetic circuit means having a gap therein and amagnetic shunt across the gap, means for pass- ..ing the materialthrough the gap, means for so producing a flux in said circuit that theflux through the shunt will approximate zero when the material is closeto standard thickness, and

means for manifesting variations of flux in the shunt resulting fromvariations in the thickness of the material. I 4. Apparatus as definedin claim 3 including circuit having a gap which varies with thethickness of the sheet of material, the core having an enlarged endportion adjacent the roll of such large size as to avoid excessivemagnetic pull of the said assembly toward the roll, means for pro.-ducing a flux in the said circuit, and means for manifesting variationsof the flux resulting from variations of the thickness of the material.

ROBERT

